Postoperative cognitive dysfunction (POCD) is the most common complication after cardiac surgery. This prospective study was conducted to investigate the mechanisms of development of POCD following cardiac surgery taking into account surgical technique (with use or no use of extracorporeal circulation). The investigators focused on the role of inflammatory and stress response to surgical procedure as potential factors involved in the pathogenesis of cognitive dysfunction. Systematic inflammatory response in patients undergoing on-pump or off-pump surgery was analyzed by measuring serum levels of C reactive protein (CRP) and occurrence of systemic inflammatory response syndrome (SIRS). Stress response to surgery was evaluated following cortisol levels and its daily variations. The degree of cognitive dysfunction was assessed based on serum levels of S100β. The effect of dexamethasone on the levels of stress and inflammatory response biomarkers, serum levels of S100β, as well as on the development of POCD was compared with control group that received normal saline.